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Altera_Forum's avatar
Altera_Forum
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13 years ago

QSYS ignores readdatavalid signal

Hi, I am currently working on an Avalon memory master that requires the readdatavalid signal to properly function. I set up the signal in QSYS but when I observed the Signaltap output for a memory read, I noticed that the readvalidsignal is always 0. Is there any reasons that can cause this? I can provide a screenshot of the signaltap output if requested.

5 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    Did you declare that the avalon master would use pipelining? It is possible that QSys would only generate the logic behind the read data valid signal when the "Maximum pending read transactions" parameter is 0.

  • Altera_Forum's avatar
    Altera_Forum
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    --- Quote Start ---

    Did you declare that the avalon master would use pipelining? It is possible that QSys would only generate the logic behind the read data valid signal when the "Maximum pending read transactions" parameter is 0.

    --- Quote End ---

    The "Maximum pending read transactions" parameter is set at 0 currently.
  • Altera_Forum's avatar
    Altera_Forum
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    Sorry I should have re-read my answer... I meant only if the parameter is not 0. When 0 it basically means there is no pipelining and the read data valid signal isn't needed. Try to set it to another value (ideally to the highest number of transactions you plan to have before getting a read value back) and see if the signal becomes valid.

  • Altera_Forum's avatar
    Altera_Forum
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    Are you sure that you are reading from a valid address? Could you do a signaltap capture of the signals on both the master and the slave, to check that the slave is receiving the read request ans replying?